Method of grinding balls.



A. E. GREENE. METHOD OF GRINDING BALLS.

11 1 110111011 r1121) JULY 20, 1911.

Patented May 14, 1912.

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Patented May 14, 1912.

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METHOD OF GRINDING BALLS.

APPLIOATION nun JULY 20, 1011 1,026,351 Patented May 14, 1912.

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[.VVENTOR.

BY I

A TTORNJZ Y3,

AUGUSTINE E. GREENE, OF HARTFORD, CONNECTICUT.

METHOD or GRINDING BALLS.

Original application filed February 20, 1911, Serial No. 609,562.

I Specification of Letters Patent.

Divided and this application filed July 20,

1911. Serial No. 689,656.

To all 1.072 om it may concern Be it known that I, AUGUSTINE E. Gnnnxn,a citizen of the United States of America,residing at Hartford,in thecounty of Hartford and State of Connecticut, have invented a new anduseful Method of Grinding Balls, the same being a divisional part of myap lication, filed in the United States Patent fiice February 20, 1911,and serially numbered 609,562, of which the following is aspecification.

My invention relates to improvements in processes or methods of makingballs of various kinds or out of various materials, and consists inimparting a varying conical rotation to a ball while in contact with arevosimilar figures luble grinding or polishing member, the rotation ofsuch ball being around a constant same manner as in the first instance,the mo-.

tion imparted to the ball during the aforesaid grinding or polishingoperations being such that the time of contact between the ball and thegrinding or polishing member at any given point of contact on the ballis approximately the same as such time of contact at any other givenpoint of contact on the ball, all as hereinafter set forth.

The primary object of my invention is to produce in an economical andexpeditious manner balls which are uniform in size, shape and finish,being perfectly spherical, and this without impairing, injuring, orchanging the properties or inherent characteristics or qualities of thematerial from which the balls are made, which material may be of-anysuitable character.

Other objects will appear in the course of the following description.

As a means of carrying my invention into effect, so as to be able toattain the objects and secure the advantages of the same, mechanism suchas I have herein illustrated may be employed, the method being wellexemplified in the operations which said mechanism is capable ofproducin In the accompanying drawings, in which refer to similar partsthroughout the several views, Figure 1 is a top plan of a machine withwhich my method can be carried out successfully; Fig. 2, an enlargedside elevation of a chuck and associated parts used in said machine, aportion of the drum which carries these members appearing in section;Fig. 3, a similar view to the preceding, as said chuck and associatedparts appear from above; Fig. 4, a vertical section taken on lines 4-4,looking in the direction of the associated arrow, in Fig. 2; Fig. 5, afront elevation of said machine; Fig. 6, a diagram illustrative of theaction of the ball-holding mechanism and having particular reference tothe method; Fig. 7, a right-hand elevation of the machine, and, Fig. 8,a vertical section taken on lines 8-8, looking in the direction of theassociated arrow, in Fig. 5.

I will commence by describing the method without relation to theparticular or detailed means or mechanism for giving it practical effectand putting it into practical use; after which I will explain suchmechanism as is shown in connection herewith.

A ball, in a more or less rough and unsymmetrical condition, is broughtunder the influence of an attracting or holding elemental force, such aselectro-magnetism (as illustated in connection herewith) or socalledsuction created by a partial vacuum produced by exhausting air from acontainer (as set forth in the application of.

which this is a divisional part, also in another divisional applicationfiled on even date with this application), and while in the power orunder the dominance of this force said ball is rotated about one axisand coincidentally oscillated upon another axis which is at right-anglesto the first, the point of intersection between the two axes being fixedor permanent and with which the true center of the finished ball coincides.

A finished ball is represented at 1, in Figs. 2, 3 and 6, and the pointjust mentioned as being that upon which the ball turns in two directionsat right-angles to each other, or the point at the intersection of thetwo axes which are arranged at rightangles to each other, is the exactcenter of said ball 1. Thus it is clear that the motion of the ball maybe described as a spiral, conical rotation of an axis of rotation, inshort, as gyratory. \Vhile the ball is thus in motion an abrader,revolved on an axis Patented May 14, 1912.

which if continued would coincide with the principal or main axis of theball or of the ball-holding and operating mechanism, is

brought into engagement with said ball, and one-half or usuallysomething more than one-half of the superficial area of the ball isground or polished by said abrader, because of the gyratory motion ofthe hall, moreover, the ball is abraded in a perfectly symmetricalmanner, so that a true hemisphere is produced, which would not be thecase if there were no gyratory motion to cause all parts of the surfacebeing abraded to receive the same amount of treatment or dressing fromthe abrader, because then those portions of such surface that were atand nearest the axial center of the abrader would be subjected to lessfrictional energy or attrition, since the speed of the abrader is lessthe nearer its axial center is approached, than those portions-of saidsurface that were farthest from such center, where the speed of saidabrader is greatest. It must be plain, therefore, that by the propermanipulation of the ball while being abraded I am able to equalize theaction of the abrader thereon. After thus abrading one-half or a littlemore of the balls surface, the abrading operation is discontinued, theball is released from the holding forceand rolled over, so to speak, topresent the other or undressed half to the abrading action, said forceis reapplied, and the abrading operation reestablished, the same resultbeing produced as before. After this the abrading operation is againdiscontinued and the ball is a second time released from the attractingor holding force. By this method, which comprises the two abradings andthe intermediate rolling, a ball which is a true sphere and thereforeperfect is theoretically produced, although in practice the ball needsto be put through the process a number of times, unless or until only aslight polishing eifect is all that is required, in order to obtain thethoroughly finished and absolutely symmetrical product.

The intermediate or rolling step in the process preferably and usuallyconsists in frictionally engaging the ball and by reason of suchengagement causing said ball to change its position relative to thematerial or mechanical holding medium therefor. This may be done eitherby moving the ball while in contact with the friction surface along suchsurface, or by moving the latter across'the engaging part of the ball,the

.ball having imparted thereto in either case 'a partial rotation in orrelative to the aforevolves and oscillates, represented at the cenvthereof.

4 tral standard 13.

ter of the ball 1, in Fig. 6, but there are also represented therein theprincipal or main axis, at 2, and, as an example merely, five positionsof the axis of rotation, at 3, which will assist in the understanding ofthe above-described method, or that part of it which involves thegyratory motion of the ball. The axis of rotation is fixed at the ballend, where it may be said to fulcrum, but is or may be flexible orjointed so that the other end can be moved longitudinally on the axis 2,as when actuated by a cam, and the lines 5 indicate such complementaryparts in the five positions of such axis; shown. In this way the axis ofrotation be- 30 comes an oscillatory axis of rotation.revolv-' ingaround the principal or main axis. I will now describe in detail themechanical meansherewith presented for carrying out the foregoingmethod, but before doing 35 so wish to state that I do not in any senselimit myself or the carrying out of my method to said means, nor do Idesire or intend to limit myself or to be limited to the exact detailsof the herein described method, since more or less departure, change ormodification from or in the prescribed course herein laid down andspecified may be made without departing from the natureof my inventionor violating the spirit Inasmuch as the machine and its severalmechanisms are included in the applications above referred to and arenot claimed herein, they will be explained as briefly as may be in orderto make clear the manner in which the method can be put to practicaluse.

i A frame is represented at 6. This frame has two head bearings 7provided with the same number of caps 9 at the right-hand end, forarotary ball-operating drum 10,, stands 11-11, at the left-hand end, foran. abrader-operating carriage 12, and a cen- J ournaled in'th'e frame6, below but in the" rear of the vertical plane of the axis of the drum10, is ashaft l4. Secured to the outer end of the shaft 14: is a drivingpulley 15 driven by a belt '16. Secured also to the shaft 14, inside ofthe pulley 15, is a gear 17 that meshes with a loose gear 18 on a studl9 projecting from the outer end of the frame head and having its axisin line with the axis of the drum 10. Secured on 12 the inner end of theshaft 14 is a gear 20. J ournaled in the center of the frame,longitudinally, is a shaft 21 which is driven from the shaft 14 throughthe medium of the gear 20 and a gear 22 secured to said '125 shaft 21. Ashort-shaft 23 is journaled in the frame head and this shaft has a gear-24 secured on its outer terminal to mesh with a large gear 25 on theouter end of the drum 10. 1311 -holder 49 is made of soft iron. end ofthis holder is cupped to fit the balls gear 25, the drum 10 is thuscaused to make one-fourth of a revolution.

The abrader-operating mechanism is driven independently by means of abelt 27 and a loose pulley 28 on a stud 29 at the left-hand end of theframe 6. The pulley .28 is'rigidly attached to a large pulley 30 whichis also loose on the stud 29, a 1d a belt 31 connects said pulley 30With the aforesaid abrader-operating mechanism in the manner hereinafterexplained, an idler 32 being provided for said belt, which idler ismounted on a stud 33 projecting from the frame above said stud 29.

Suitably journaled in the drum 10 and extending beyond both ends thereofare four spindles 34. These spindles are arranged at equal distancesfrom the longitudinal center of the drum and at equal distances fromeach other, and have secured on their outer ends pinions 35 which meshwith the constantly revolving gear 17. Each spindle 34 is provided atits inner terminal with a yoke 36, and slidingly mounted on such spindleis a cam-sleeve 37. A spring 38 encircles each spindle 34 between itsyoke 36 and a washer 39 which bears against projecting parts of thecam-sleeve 37 on said spindle, and retains said sleeve with its camfaceagainst an abutment in the form of a roll 40 which is in the path ofsaid camface. There is a roll 4.0 for each cam-sleeve 37, and such rollis mounted on a stud 41 carried by a supporting bracket 42 that isrigidly attached to the drum in proper relation to the adjacentcam-face. Pivotally attached at 43-43 to each cam-sleeve 47 is a yoke44, and pivotally attached at 45 to the left-hand terminal of said yokeis a chuck 46. Each chuck 46 has two arms 47, at the end opposite thatwhich is pivoted to the supporting yoke 44 therefor, and these arms arepivoted at 4848 to the free terminals of the associated yoke 36, insideof the arms or branches of the same. Each chuck has, furthermore, a core49 which projects from the barrel or spool of said chuck between thearms 47 and constitutes the actual holder for the balls. The "ore or Theexposed and form a good and suflicient contact or connection therewith.

The roll 40 in each case is so situated that the contacting cam-sleeve37 can never slide on its spindle 34 far enough toward the drum 10 toallow the axis of the associated chuck 46 to coincide with the axis ofsaid spindle, and. since said chuck swings at one end on an axis,represented by the pivots 48, the angle of inclination of the chucka'xis changes as the parts revolve with said spindle, because saidsleeve is then reciprocated by reason of the contact between itscam-face and said roll and through the medium of the connecting yoke 44.Thus the point of intersection between the spindle axis, which is theprincipal or main axis corresponding to the line 2 in Fig. 6, and thesecondary axis or the axis upon which the chuck oscillates, representedby the pivots 48, because the point about and upon which the revolutionand the oscillation of the chuck take place, and is the center of theerfect ball, it being understood that the distance from such point tothe center of the holder 49 is equal to one-half the diameter of suchball. The axis of the chuck is represented by the lines 3 and theconnecting or longitudinal axis of the yoke 44 by the lines 5, in Fig.6, in the five different possible positions given them by the cam actingagainst the roll and moving the adjacent end of said yoke axis along thespindle axis. By this means and in this manner a ball in the holderreceives the motions already very fully described.

Inasmuch as electro-magnetism is the active natural agent or mediumherein represented as being employed for retaining the balls firmly andsecurely in the holders 49, I will next explain the means for applyingthe same. The drum 10 is provided with a commutator 50 for each chu'ck'46, and a brush 51 is provided for each commutator, such brush dependingfrom an insulating .bracket 52 mounted on the inner cap 9. The bracket52 is provided with adjusting screws 53 for the brushes 51 and thelatter with binding-posts 54, as usual. \Vircs 55 lead from the bindingposts 54 to a suitable source of electrical energy, indicated at 56,.Fig. 1, and a wire 57 leads from such source to a non-insulated bindingpost 58 on the outer cap 9. Each commutator is connected, in thecustomary manner, by a wire 59 with a binding-post 60 set in aninsulatedbracket 61 attached to the drum adjacent to me of the spindles 34, and ashort wire 62 connects such binding-post with a brush 63. Each brush 63is adjustably held in one of the brackets 61 by a screw '64. Secured toeach spindle 34, with an insulating ring 65 between, is a contact ring66 against which one of the brushes 63 bears. A wire 67 leads from eachcontact ring 66 to a binding-post 68 at the inner end of one of the armsor branches of the yoke 36 which is at the inner terminal of the spindle34 upon which such ring is mounted, said wire passing from such ringthrough radial openings in the associated insulating ring 65 and spindleto a central longitudinal passageway 69 in said spindle, as shown inFig. 4, thence through such passageway to said yoke, out through asuitable openingin the yoke, and along the outside of the yoke arm whichsupports said binding-post to the' latter, as best shown in Fig. 3, theaforesaid opening in the yoke being represented by dotted lines at 70. Ashort wire 71 connects the binding-post 68 with a binding-post 72 on thechuck 46in this combination, and the circuit to the frame is completedthrough a short wire 73 which connects two binding-posts 74 and 75 alsoon said chuck, but the binding-post 75 being non-insulated. Thebinding-posts 72 and 74 are the terminals of-the electromagnet whichforms part of the chuck 46. Thus the circuit from the source of energyat 56 to any chuck 46 and back to such source is formed by the properwire 55, brush 51 and commutator 50, and the wires 59 and 62, brush 63,ring 66, and the wires 67, 71 and .73 in the combination, the frame ofthe machine, and the wire 57.

The arrangement of the commutators '50 and the timing of the drum 10 aresuch that each chuck 46 or its holder 49 is magnetized and demagnetizedfour times at every revoluticn of said drum, but all of said holders arenot magnetized and demagnetized together. When any holder 49 ismagnetized it attracts to itself and holds securely any ball that is agood subject for magnetic attraction when brought into the field of suchattraction emanating from such holder, and releases said ball upon beingdemagnetized;

For the purpose of impartingtlinecessary independent rolling motion orhalf revolution to the "ball when it passes from one abrader to theother, as yet to be more fully explained, so that theunabraded portionor side will be presented to the second abrader, a piece of felt orother suitable material to form a friction member 76 is attached to theright-hand face of the stand ard 13 near the top.. The friction member76 occupies a position such that the center of its exposed or workingface approximately coincides with the top of the ver tical diameter ofthe circle described by the left-hand end of the horizontal diameter ofa ball held by any one of the chucks 46, but encro-aches somewhat on thevertical plane of such circle. Such being the case, a ball held by oneof the chucks 46, if such chuck were energized, would be carried pastalthough frictionally engaging the member 76 without being affectedthereby, but if the energy be cut off from such chuck after it hasbrought said ball into rubbing contact with said friction member,-thelatter will impart an independent rolling motion to said ball, or, inother words, will rotate said ball in its holder, the amount of suchrotation depending upon the length of the friction 'member and thelength of time the chuck remains unenergized. This is exactly what isdone in practice, and, since the ball is held so tightly by the frictionmember in the cupped end of the operating holder 49 that said ballcannot get out of said holder, the ball rolls or is rolled in theholder, and when it has been turned half over or half way around thereinthe chuck is energized again and carries the ball wit out furtherindependent movement or moti 11 off of and away from said member 76.Although the chuck does not stop rotating while the ball is beingcarried past the member 76, the motion of the chuck in no wiseinterferes with the independent rolling of the ball, but ratherfacilitates such action.

Passin r to the abrader-operating mechanism which includes the carriage12, it will be observed that such carriage is reciprocated by means of acam 100 secured on the shaft 21 between the stands 11. This cam has acam-groove 77 therein to receive an anti-friction roll 78mounted on astud 7 9 set in the bottom'of the carriage 12. The form or shape of thecam-groove 77 is such that at.,.eve'iy revolution of the cam 100 thecarriage, through the medium of the roll 78 and stud 79, 15 caused totravel from one end of its course to the other and back again. The othermembers of the abrader-operating mechanism consist of two parallelspindles80 arranged to revolve side by side in two pairs of bearings 81and under two pairs of caps 82 at the opposite ends of the carriage 12,and of the attached and associated elements described below. Thespindles 80 do not rest directly in the lefthand bearings 81 and caps82, but in collars 83-"83 which are tapped into said bearings and caps.The spindles are not only capab of revolving in their bearings, but theymay also be reciprocated therein. Said spindles extend beyond theleft-hand bearings 81, and the belt 31 passes under the pulley 30, overthese extending portions of the spindles, and

under the idler 32, so that the spindles are.

driven in the same direction at a great speed by said belt and rotarymembers and'by the belt 27 and the pulley 38. These pulleyextensions, asthey may be called, shown at 84-84, of the spindles 80, are ofsutlicient length to permit of the required amount 01 longitudinalmovement without the belt 31 running off. Attached to the inner terminalof each spindle 80 is a head 85 which receives the stem of a suitableholder 86 for an abrader 87, a set-screw 88 being employed in thecustomary manner to assist in securing said stem to said head and toafford adjustment for said stem. The abraders 87 are made of anysuitable grinding or polishing material. A. collar 89 is secured to eachof the spindles 80 in position to bear against a .innermost independentpositions with a force that may be varied by screwing the collars 83 inor out. The springs 90 are sutliciently strong and stiff to hold theabraders 87 to their work, when the carriage 12 is in its advancedposition, yet such springs afford yielding means for the spindles 80whereby said abraders cannot be forced too hard against the balls, asmight otherwise happen occasionally in the event the balls should be toolarge. As previously intimated, the ball-extensions 84 are long enoughto enable the carriage to complete its inward travel withoutdisconnecting the motive power, also, of course, to permit of whateverlittle independent movement there may be longitudinally on the part ofthe spindles 80. The base ,of the carriage 12 is flanged at 91 to fitand slide in guide-ways on the stands 11, such guide-ways consisting inpart of plates 92. The cam-groove 77 is so shaped that a dwell isproduced at each end of the throw of the cam 100, so that, at eachrevolution of said cam, the carriage 12 is actuated forward and backwardand held during parts of such revolution in both of its extremepositions. The abraders 87 are hollowed or recessed in the centers oftheir working faces to receive the balls, in much.

the same manner as are the holders 49, and when the abrader holders 86are properly adjusted in the heads 85 and the collars 89 are against thecontiguous bearings 81 and caps 82, the cam 100 as it revolves advancesthe parts, until the centers of the cupped portions of said abradcrscoincide or approximately coincide with the'circular path at theright-hand. ends of the horizontal diameters of the finished ballscarried by the chucks 46. In other words, the point of intersectionbetween the oscillatory axis of rotation and the main or principal axisaround which such oscillatory axis revolves, of any chuck whenjuxtaposed to an advanced abrader, that is, of a chuck which is in suchposition that its main axis it continued would coincide with the axis ofsaid abrader is the same distance fromthe center of the concavity insaid abrader as it is from the centerof the concavity of the holder 49of said chuck.

Although this machine is provided with automatic means for feeding theballs, only a trough or raceway 93 is herein shown, since that is allthat is needed for a clear understanding of the subject matter of thepresent application. The raceway 93 is supported from the floor by amember 94 which is braced from the frame 6, as shown at 95, in Pig. 8.The raceway 93 curves rearwvardly and slantsdownwardly from the member94, to open at its back end toward the orbit of the holders 49 and at apoliit which is below the advanced position of the forward abrader 87 orof the working face of said abrader. This raceway constitutes part ofthe almve-menticned ball-feeding means, and is the member that receivesthe balls an'didelivers them to the ball holders.

'lheoperation of the machine described above, which involves or includesmy method, is as follows, said method in the followmg description beingset forth in fuller detalls than heretofore. Having connected both endsof the machine with the power, the revolving members are set in motion,rotating in the directions indicated by the arrows associated therewith,andsome of such members revolving constantly and some intermittently, asalreadymade plain, and as about to be further explained. The gear 17 onthe shaft 14 with the pulley 15, through the medium of the intermediategear 18 and the pinions 35, causes the four spindles 34 to revolveconstantly; and the gear 20, also on said shaft and through the mediumof the gear 22, causes the shaft 21 to revolve constantly with the cam100 thereon. Coincidentally, the spindles 80 are driven constantly bythe belts 31 and 27, but generally in the opposite direction to that ofthe spindles 84. Assuming, now, thatthere is a ball in the raceway 93and that balls are being delivered to said raceway, by the time thefirst ball arrives at the open rear end which is the discharge 01'delivery end of said raceway there is a chuck 46 in position adjacent tosuch end, with its holder 49 energized, to pick said ball from saidraceway and securely hold it, the electric circuit to and through suchchuck being closed at this time by reason of the fact that thecommutator 50 which belongs in said circuit has one of its electricalcontacting segments in contact with its brush 51. Although the spindle34 with which the aforesaid chuck is connected is revolving the circuitis not interfered with because of the presence of one of the contactrings 66 on such spindle, and the connection afforded by the brush 63which bears on said rin \Vhile held securely by theenergized chul: 46,which for convenience will be called the first chuck, the ball iscarried thereby from the receiving position to the first abradingposition in line with the forward abrader 87, which abrader meanwhile isin retracted position. The first chuck with the ball is moved into thenew position by reason of the fact that the constantly-revolving shaft21 imparts to the shaft 23, through the medium of the clutch 26,one-half of a revolution, and said shaft 23 in turn with its gear 24imparts one-fourth of a revolution to the gear 25 and the drum 10 whichcarries said chuck; and said chuck with the ball is left in suchposition because, by the time or at the time it arrives there, saidclutch releases said shaft 23 and the movement of said drum ceases.Immediately the cam 100 advances the carriage 12 and thrusts the forwardabrader 87 against the ball now held and rotated by the first chuck inthe first abrading position, the ball being rotated in the peculiarmanner previously set forth at length. One side of the ball is subjectedto the action of the forward abrader until the latter is withdrawn, whenthe clutch operates to give the drum another quarter turn. Meanwhile thesecond chuck has picked the second ball from the raceway 93 at thereceiving position.

Just before the first chuck moves-from the first abrading positionadjacent to the forward abrader to the second abrading position adjacentto the rear abrader, the cam 100, which retains the forward abrader inadvanced position during the abrading op eration, retracts the carriage12 and so takes the abraders from the field of action, and said camkeeps them out of such field until the first chuck arrives at the secondabrading position, when, of course, the second chuck will be in thefirst abrading position.

Upon the second quarter of the revolution of the drum 10, the first ballis caused to traverse the friction member 76, and just after said ballreaches said member the first chuck is demagnetized, so as to enable theball to roll in its holder or to be rolled therein by frictional contactwith said member, and just before said ball leaves said member saidchuck is magnetized again. The first ball, thus turned half way over oraround so as to present the undressed side to the rear abrader, is nextleft at thesecond abrading position, when for a second time the clutch26 free the shaft 23, and the abraders are advanced and operate thistime on two balls, the rear abrader operating on the first ball attachedto the first chuck and the forward'abrader operating on the second ballattached to the second chuck. It is thus seen that one side of each ballis dressed by the forward abrader, and that the other side of each ballis dressed by the rear abrader. For the second time the abraders areretracted, and then the drum makes the third quarter of its revolution,with the result that the first ball is dropped from the now demagnetizedchuck, the second ball is carried 'to the second abrading position, be-

ing turned half way around on the way, and the third ball, which thethird chuck has already picked, is brought to the first abradingposition. With the completion of the revolutlon of the drum, during thelast quarter of which the second ball is dropped, the

third ball is carried to the second abrading position and the fourthball held by the fourth chuck to the first abrading position, and thefirst chuck is again magnetized so that it can pick the fourth ball, onecycle of the machine is complete, provided such cycle" start with thepicking of the first ball by the first chuck, in accordance with theforegoing description. During this cycle the drum operates at fourregular intervals, the carriage advances and retreats four times, andeach chuck is demagnetized twice, once when it passes the frictionmember 76, and once again when it drops the ball after the secondabrading.

The balls may be run through the machine a number of times or until theyare reduced to the exact size desired or are finished or polished to therequired degree of nicety. With this machine balls of any material thatis subject to magnetic attract-ion can be handled, but the same methodcan be carried out with the aid of a machine equipped with means forhandling balls of other materials.

What I claim as my invention, and desire to secure by Letters Patent,is-

1. A method of abrading spherical objects, consisting inv imparting anorbital gyratory motion to an object on its own center while subjectedto an abrading action.

2. A method of abrading spherical objects, consisting in imparting acombined rotary and orbital oscillatory motion to an object,on its owncent-er while subjected to an abrading action.

3. A method of abrading spherical objects, consisting in imparting avarying conical orbital rotation to an object on its own center whilesubjected to an abrading action.

,4. A method of abrading spherical objects, consisting in applying anelemental force to an object to hold the same, in imparting a combinedrotary and orbital oscillatory mot-ion to said object on its own centerwhile thus held, and in subjecting the moving object to an abradingaction.

5. A method of abrading spherical ob jects, consisting in applying anelemental force to an object to holdthe same, in imparting a combinedrotary and oscillatory motion to said object while-thu held, insubjecting the moving object to an abrading action, in releasing andturning said object independently, in reapplying said force andrestoring said combined rotary and oscillatory motion to the object, andin again subjecting the moving object to said abrading jects, consistingin g'yrating an object while subjected to an abrading action, and ininterinediately partially turning such object on one of its axes.

8. A method of abrading spherical objects, consisting in gyrating anobject While subjected to an abrading action on one portion of itssurface, and in partially turning said object to present another portionfor such action.

AUGUSTINE E. GREENE. \Vitnesscs A. C. FAIRBANKS, F. A. CUTTER.

